Oil fields in the Devonian terrigenous sediments in the east of the East European Platform play a large role in ensuring a high level of hydrocarbon production. At the first stages of the development of the oil industry, the production of liquid hydrocarbons from deposits was carried out from plicative traps associated with extended swells, such as the Tuymazinsky-Bavlinsky, Serafimovsky-Baltaevsky and Shkapovsky arched uplift. The second stage in the development of oil production from these deposits began after the discovery of large oil accumulation zones linearly elongated from southwest to northeast, confined to the Devonian consedimentary graben-like troughs (Sergeevsko-Demsky, Tavtimanovo-Urshaksky and others) formed in the Lower Timan time. They controlled mainly both large and medium-sized deposits. In parallel with them, oil accumulation zones were discovered associated with post-sedimentary graben-like troughs, horst-like structures and buried Devonian terraces. The identified oil reserves in them were quantitatively inferior compared to the previous zones. Tectonic disturbances, in addition to participating in screening and formation of structures, took part in the movement of hydrocarbons, mineralized and hydrothermal waters from bottom to top along the section. Reservoir fluids, in combination with rock pressure and temperature, influenced the capacitive properties of Devonian quartz silt-sand reservoirs. The changes were studied using instrumental methods, including optical and electron microscopy. The latter represent high-tech core studies that reveal a number of structural features of the rocks being studied. Firstly, this is the presence of newly formed quartz of small size (grain size from 1 to 10 micrometers), similar in size to the pelitic fraction in silty-sandy rocks, consisting of clay minerals. Secondly, the presence of ribbon crystals of illite was revealed, which, like quartz microcrystals, retain the volume of pore space. These features in the lithology of reservoirs were first established in silt-sand reservoirs of the terrigenous Devonian in sections of wells drilled near tectonic disturbances. Identifying them in reservoirs will allow more accurate assessment of hydrocarbon reserves.
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